Testing the magnetic qualities of materials.



PATENTED NOV. 1, 1904.

F. HOLDEN. TESTING THE MAGNETIC QUALITIES OF MATERIALS.

APPLICATION FILED JULY 6. 1903.

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lnventorfi Frank I-Iolden.

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PATENTED NOV. 1, 1904. P. HOLDEN. I TESTING'THE MAGNETIC QU-ALITIES OFMATERIALS.

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APPLICATION FILED JULY 6. 1903.

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4 Frank Holden mg Atty UNITED STATES Patented November 1, 1904.

PATENT Orricn.

FRANK HOLDEN, OF RUGBY, ENGLAND, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK.

TESTING THE MAGNETIC QUALITIES OF MATERIALS.

SPECIFICATION formingpart of Letters Patent No. 773,937, dated November1, 1904.

Application filed July 6, 1903- Serial No. 164,279. (No model.)

To all whom, itvnayconcern:

Be it known that I, FRANK HOLDEN, a citi- Zen of the United States ofAmerica, residing at Rugby, England, have invented certainnew and usefulImprovements in Testing the h Iagnetic Qualities of Materials, of whichthe following is a specification.

My invention relates to improvements in apparatus for determining themagnetic prop- IO erties of metals, such as iron and steel, for

use in dynamos, transformers, and other electromagnetic appliances, andhas for its object to provide an apparatus whereby such metals in theform of bulk samples may be tested in 5 a simple and expeditious manner.

The features of novelty characteristic of my invention I have endeavoredto point out with particularity in the appended claims.

For a complete understanding of my inven- Zv tion, both as to itsconstruction and mode of operation, reference is to be had to thefollowing description, taken in connection with the accompanyingdrawings, in which Figure 1 is an elevation, partly in section,

5 of an instrument embodying my invention. Fig. 2 is a plan view of theinstrument, while Fig. 3 is a more or less conventional and diagrammaticview for illustrating the elements of the invention.

3 In carrying my invention into practice I provide a uniform orpractically uniform magnetic field, and in this magnetic field I suspenda movable closed conducting-circuit of such form as to allow the sampleto be tested to be linked with it. Variations of magnetism produced inthe sample by a magnetizing-coil generate currents which operate toproduce a displacement of the conductor in the magnetic field, whichdisplacement is pro- 4 portional to the change in magnetic flux of thetest sample. As shown in Fig. 1, the uniform magnetic field is providedby a permanent magnet 1, the poles of which are spread out and partlysurround a fixed iron cylinder 2, but without touching the latter. Inthe space between the cylinder 2 and the polepieces of the magnet 1 aclosed conducting circuit or coil 3, of copper or other suitable metalwire, is supported so as to allow free rotation of the same. The supportmay be 5 afforded by any appropriate means, such as a silk suspensionfiber or by a pivot, as indicated at 4. The coil 3 extends down belowthe cylinder 2 in the form of a suitablyshaped loop, such as indicatedat 5. This loop surrounds a magnetizing-coil (indicated in dotted linesat 6 in Fig. 2) and is of sufficient diameter so that it may rotatethrough a considerable angle without coming into contact with the coil.The bar to be tested, after being brought to the proper size, isinserted in the coil, as indicated at 7 The magnetic circuit of the baris completed by the base 8, which itself is of magnetic material. Thearrangement thus described as embodied in a 5 practical instrument isshown in a somewhat simpler manner in Fig. 3, in which the polepieces ofthe exciting-magnet are represented at 9 and 10, the movable coil at 11,and the test-piece, in the present instance in the form 7 of a ring,linked about the coil 11. The exciting-winding for the test-piece isrepresented at 13.

In making a measurement with the instrument a known current is passedthrough the exciting-coil and then either interrupted or reversed. Thecurrent induced in the closed conductor causes the latter to move in theuniform magnetic field through an angle proportional to the change offlux produced through the closed conductor by the test-piece. When thecoil has come to rest, its angle of deflection may be measured by asuitable pointer, such as at 14c in Fig. 2. This angle, as beforementioned, is proportional to the change 5 of flux in the sample. It isread, however, while the pointer is at rest and not, as in the case ofthe ordinary ballistic galvanometer, when the pointer has reached themaximum deflection in an oscillating movement. 9

In the foregoing description and accompanying drawings I haveillustrated but-one of the various forms which my invention may assume.I therefore do not wish to be limited to the exact form shown anddescribed, since it Will be evident to one skilled in the art thatvarious modifications thereof can be made Without departing from thespirit of my invention.

WVhat I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. In a measuring instrument, the combination of means for producing auniform magnetic field, a closed conductor suspended so as to move inthe magnetic field, and a testpiece linked through the circuit of theconductor.

2. In an instrument, the combination of means for producing a magneticfield, a closed conductor arranged to move in the magnetic field, atest-piece arranged so that its magnetic circuit is interlinked With thecircuit of said closed conductor, and means for varying the flux in saidtest-piece.

3. In an instrument for testing the magnetic qualities of iron. or othermagnetic material, the combination of a closed conductor, means forproviding a substantially uniform magnetic field through Which saidconductor is adapted to move, and a magnetic circuit, including thepiece to be tested, interlinked With said movable conductor.

4. In an instrument for testing the magnetic qualities of a sample ofiron or other metal, the combination of a closed conductor, and meansfor generating in said conductor two electromotive forces, one due tovariations of flux in the test sample and the other due to motion of theconductor.

In Witness whereof I have hereunto set my hand this 23d day of June,1903.

FRANK HOLDEN.

IVitnesses:

H. D. JAMEsoN, F. L. BAND.

